A liquid crystal display (LCD) used in a vehicle for displaying a map for. vehicle navigation or a television program. The LCD includes an LCD panel, a backlight unit, and an external frame as main components. The external frame houses the LCD panel and the backlight unit. The LCD panel is constructed of two transparent plates and liquid crystal that is filled between the transparent plates. In recent years, glass substrates are used for the transparent plates. Circuit patterns are formed on the glass substrate outside a display area by print wiring means. A driver IC for the LCD panel is mounted in the circuit pattern formed area. In such a display, the circuit patterns on the glass substrate are connected to an external display control device via a flexible printed circuit board (FPC).
Because high-frequency control signals are inputted to the LCD panel, unnecessary radiating noises (electromagnetic waves) are produced. Display devices having structures for reducing such unnecessary radiating noises are proposed in JP-A-7-92450, JP-A-10-244054, and JP-A-2002-91327. In JP- A-7-92450, the LCD device has a source circuit board and a gate circuit board around a crystal display panel. The liquid crystal display panel is housed inside a metal external frame. A ferrite is arranged the periphery of the liquid crystal display panel and sandwiched between the liquid crystal display panel and the external frame. As a result, unnecessary radiating noises produced in the source circuit board and the gate circuit board do not leak outside.
In JP-A-10-244054, a transparent shield member is arranged on a back surface of a liquid crystal display panel to reduce unnecessary radiating noises produced in the liquid crystal display panel leak outside.
In JP-A-2002-91327, a liquid crystal display device is configured that a liquid crystal display panel and a backlight unit housed in an external frame. A transparent electrode is formed on an entire top surface of a polarizer of the liquid crystal panel. An entire display surface of the liquid crystal display panel is shielded from electromagnetic waves by connecting the transparent electrode with a printed circuit board arranged on a back side of the crystal display panel.
When a circuit pattern on the glass substrate is connected with an external display control device via a FPC, high frequency control signals pass through the FPC. Therefore, unnecessary radiating noises are produced from the FPC. The liquid crystal display device for a vehicle is arranged around a radio turner or a television tuner. Thus, problems including noises in radio sound or television picture distortion are caused by the radiating noises produced from the liquid crystal display device.
A ground is provided in the flexible printed board for connecting to a ground of the display control device. However, this provides little effect on reduction of the unnecessary radiating noises. Therefore, the FPC is covered with a shielding layer and the shielding layer. is connected. to the ground of the display control device via the ground of the FPC.
However, a method including covering the FPC with the shielding layer still provides little effect on shielding of the unnecessary radiating noises. This is because the ground is unstable. If the ground has a large area, it will be stable. However, the ground of the FPC is formed in a line. Namely, the ground does not have a large area for properly reducing electrical charge produced in the shielding layer. As a result, the unnecessary radiating noises are not effectively reduced.